The process for car owners who want to install an air bag switch, according to the government:

_Starting Dec. 19, motorists can get a request form from the National Highway Traffic Safety Administration and at some dealerships, repair shops and state motor vehicle offices.

_Motorists will be required to read a brochure about air bags.

_They will sign the paperwork under penalty of perjury, certifying that they fit into one of several higher-risk categories, and send it back to the government.

_NHTSA will send the owner an authorization letter for the mechanic to install the switch.

_Switches will be installed starting Jan. 19.

_Automakers such as General Motors Corp. and Ford Motor Co. are recommending that consumers get switches at dealerships, since those switches would be specifically tailored for each of their models. However, the government is not specifying who should do the work.